[Federal Register Volume 79, Number 113 (Thursday, June 12, 2014)]
[Rules and Regulations]
[Pages 33677-33679]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-13665]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2013-0898 Special Conditions No. 25-526-SC]
Special Conditions: Airbus Model A350-900 Series Airplane;
Composite Fuselage In-Flight Fire/Flammability Resistance
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for Airbus Model A350-900
series airplanes. These airplanes will have a novel or unusual design
feature associated with the in-flight fire and flammability resistance
of the composite fuselage. Experience has shown that eliminating fire
propagation on the surface of interior and insulating materials
enhances survivability since the threats from an in-flight fire (e.g.,
toxic gas emission and smoke
[[Page 33678]]
obscuration) are typically by-products of a propagating fire. The
Airbus Model A350-900 series airplanes must provide protection against
an in-flight fire propagating along the surface of the fuselage.
Special conditions are needed to address this design feature. The
applicable airworthiness regulations do not contain adequate or
appropriate safety standards for this design feature. These special
conditions contain the additional safety standards that the
Administrator considers necessary to establish a level of safety
equivalent to that established by the existing airworthiness standards.
DATES: Effective July 14, 2014.
FOR FURTHER INFORMATION CONTACT: Jeff Gardlin, FAA, Airframe/Cabin
Safety, ANM-115, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue SW., Renton, Washington, 98057-3356;
telephone (425) 227-2136; facsimile (425) 227-1320.
SUPPLEMENTARY INFORMATION:
Background
On August 25, 2008, Airbus applied for a type certificate for their
new Model A350-900 series airplane. Later, Airbus requested and the FAA
approved an extension to the application for FAA type certification to
June 28, 2009. The Model A350-900 series has a conventional layout with
twin wing-mounted Rolls Royce Trent engines. It features a twin aisle
9-abreast economy class layout, and accommodates side-by-side placement
of LD-3 containers in the cargo compartment. The basic Model A350-900
series configuration will accommodate 315 passengers in a standard two-
class arrangement. The design cruise speed is Mach 0.85 with a Maximum
Take-Off Weight of 602,000 lbs.
Experience has shown that eliminating fire propagation on the
surface of interior and insulating materials enhances survivability
since the threats from an in-flight fire (e.g., toxic gas emission and
smoke obscuration) are typically by-products of a propagating fire. The
Airbus Model A350-900 series airplane must provide protection against
an in-flight fire propagating along the surface of the fuselage.
In the past, fatal in-flight fires have originated in inaccessible
areas of the aircraft where the thermal/acoustic insulation located
adjacent to the aluminium aircraft skin has been the path for flame
propagation and fire growth. Concern over the fire performance of
thermal/acoustic insulation was initially raised by five incidents in
the 1990's which revealed unexpected flame spread along the insulation
film covering material. In all cases, the ignition source was
relatively modest and, in most cases, was electrical in origin (e.g.,
electrical short circuit, arcing caused by chafed wiring, ruptured
ballast case). From 1972 until 2003 these materials were required to
comply with a basic ``Bunsen burner'' requirement per Title 14 Code of
Federal Regulations (14 CFR) 25.853(a), 25.855(d), and part 25,
Appendix F, part I, paragraph (a)(1)(ii). These requirements prescribed
that insulation materials must be self-extinguishing after having been
subjected to the flame of a Bunsen burner for 12 seconds, in accordance
with the procedures defined in part 25, Appendix F, part I, paragraph
(b)(4). The average burn was not to exceed eight inches and the average
flame time after removal of the flame source was not to exceed 15
seconds. Drippings from the test specimen were not to continue to flame
for more than an average of five seconds after falling.
Further concern with the flammability of thermal/acoustic
insulation was raised by the Transportation Safety Board (TSB) of
Canada during their investigation of the fatal Swiss Air MD-11 in-
flight fire accident that occurred in September 1998 and involved 229
fatalities. TSB investigators reported that the fatal fire appeared to
have been confined to the area above the cockpit and forward cabin
ceiling and involved the insulation blankets. On August 21, 2001, the
TSB recommended that flammability standards for interior materials
should be based on realistic ignition scenarios and prevent the use of
materials that sustain or propagate a fire.
In 1996, the FAA Technical Center began a program to develop new
fire test criteria for insulation films directly relating to the
resistance of in-flight fire propagation. The current test standard was
evaluated as well as another small-scale test method that has been used
by airplane manufacturers to evaluate flame propagation on thermal/
acoustic insulation materials. An inter-laboratory comparison of these
methods revealed a number of deficiencies. Other small-scale tests
developed by the FAA Technical Center did demonstrate that some
insulation films would ignite and propagate flame in a confined space.
As a result, a series of large-scale fire tests were conducted in a
mock-up of the attic area above the passenger cabin ceiling. In a
confined space, ignition and flame propagation may occur because of
more extensive radiating heat and the trapping of melted film/scrim.
Temperature (heat release) data was recorded and the degree of flame
propagation was observed from the large-scale tests. A radiant panel
test standard for flooring materials was a test method that provided
good correlation to the large-scale model. The test method involved
subjecting a material to a pilot flame while the material is heated by
a radiant panel.
The previously described development program resulted in a new test
method (radiant panel test) and test criteria specifically established
for improving the in-flight fire ignition/flame propagation of thermal/
acoustic insulation materials. A new part 25 airworthiness standard,
Sec. 25.856, became effective in September 2003, Amendment 25-111,
requiring that all thermal/acoustic insulation materials installed in
the fuselage must comply to this flammability and flame propagation
requirement. The standards are intended to ``reduce the incidence and
severity of cabin fires, particularly those ignited in inaccessible
areas where thermal acoustic insulation materials are typically
installed.''
Type Certification Basis
Under Title 14, Code of Federal Regulations (14 CFR) 21.17, Airbus
must show that the Model A350-900 series airplane meets the applicable
provisions of 14 CFR part 25, as amended by Amendments 25-1 through 25-
129.
If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Model A350-900 series because of a
novel or unusual design feature, special conditions are prescribed
under Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same or similar
novel or unusual design feature, the special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Model A350-900 series must comply with the fuel-vent
and exhaust-emission requirements of 14 CFR part 34 and the noise-
certification requirements of 14 CFR part 36. The FAA must issue a
finding of regulatory adequacy under Sec. 611 of Public Law 92-574,
the ``Noise Control Act of 1972.''
The FAA issues special conditions, as defined in 14 CFR 11.19,
under Sec. 11.38, and they become part of the type-certification basis
under Sec. 21.17(a)(2).
[[Page 33679]]
Novel or Unusual Design Features
The Airbus Model A350-900 series airplane incorporates the
following novel or unusual design features: Fuselage fabricated with
composite materials.
Discussion
The Airbus Model A350-900 series airplane makes extensive use of
composite materials in the fabrication of the majority of the wing,
fuselage skin, stringers, spars, and most other structural elements of
all major sub-assemblies of the airplane. Despite the major change from
aluminum to composite material for the fuselage, the Model A350-900
series must have in-flight survivability such that the composite
fuselage does not propagate a fire. A methodology for assessing the in-
flight fire survivability of an all-composite fuselage is therefore
needed.
The FAA believes that one way to assess the survivability within
the cabin of the Model A350-900 series airplane is to conduct large-
scale tests. This large-scale test would utilize a mock-up of an Airbus
Model A350-900 series airplane fuselage skin/structure section of
sufficient size to assess any tendency for fire propagation. The fire
threat used to represent the realistic ignition source in the airplane
would consist of a 4'' x 4'' x 9'' polyurethane foam block and 10 ml of
Heptane. This ignition source provides approximately three minutes of
flame time and would be positioned at various points and orientations
within the mocked up installation to impinge on those areas of the
fuselage considered to be most crucial.
This fire threat was established based on an assessment of a range
of potential ignition sources, coupled with possible contamination of
materials. The FAA considers this a severe fire threat, encompassing a
variety of scenarios. However, should ignition or fire sources of a
greater severity be identified, the special condition or its method of
compliance would need to be modified in order to take the more severe
threat into account.
These special conditions contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
Discussion of Comments
Notice of proposed special conditions No. 25-13-33-SC for the
Airbus Model A350-900 series airplanes was published in the Federal
Register on November 15, 2013 (78FR68775). No comments were received,
and the special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions apply to Airbus Model
A350-900 series airplanes. Should Airbus apply later for a change to
the type certificate to include another model incorporating the same
novel or unusual design feature, the special conditions would apply to
that model as well.
Conclusion
This action affects only certain novel or unusual design features
on the Airbus Model A350-900 series airplanes. It is not a rule of
general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
The Special Conditions
0
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for Airbus Model A350-900 series
airplanes.
Composite Fuselage In-Flight Fire/Flammability Resistance
In addition to the requirements of Sec. 25.853(a) governing
material flammability, the following special condition applies:
The Airbus Model A350 composite fuselage structure must be shown to
be resistant to flame propagation under the fire threat used to develop
Sec. 25.856(a). If products of combustion are observed beyond the test
heat source, they must be evaluated and found acceptable.
Issued in Renton, Washington, on: April 22, 2014.
Jeffrey E. Duven,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2014-13665 Filed 6-11-14; 8:45 am]
BILLING CODE 4910-13-P